Soft-error characteristics in bipolar memory cells with smallcritical charge

The alpha-particle-induced soft-error mechanism in a high-speed bipolar static RAM (SRAM) which is used for mainframe computers is investigated using a three-dimensional (3-D) device and a circuit simulator. It is shown that a constant critical charge for the memory cell does not exist. This is because the memory cell's soft-error sensitivities to the charges collected at the base and collector of the cell transistor are different due to the difference in time constants of the base and collector. To take into account this sensitivity difference in the soft-error rate simulation, an effective-charge model is proposed. This model incorporates weight coefficients that express the memory cell's soft-error sensitivities to the charges collected at the base and collector. Accelerated soft-error rates of the 4-kb SRAMs are simulated using the effective-charge model     

Capillary-assembled microchip for universal integration of various chemical functions onto a single microfluidic device

A novel concept for assembling various chemical functions onto a single microfluidic device is proposed. The concept, called a capillary-assembled microchip, involves embedding chemically functionalized capillaries into a lattice microchannel network fabricated on poly(dimethylsiloxane) (PDMS). The network has the same channel dimensions as the outer dimensions of the capillaries. In this paper, we focus on square capillaries to be embedded into a PDMS microchannel network having a square cross section. The combination of hard glass square capillary and soft square PDMS channel allows successful fabrication of a microfluidic device without any solution leakage, and which can use diffusion-based two-solution mixing. Two different types of chemically modified capillaries, an ion-sensing capillary and a pH-sensing capillary, are prepared by coating a hydrophobic plasticized poly(vinyl chloride) membrane and a hydrophilic poly(ethyleneglycol) membrane containing functional molecules onto the inner surface of capillaries. Then, they are cut into appropriate lengths and arranged on a single microchip to prepare a dual-analyte sensing system. The concept proposed here offers advantages inherent to using a planar microfluidic device and of chemical functionality of immobilized molecules. Therefore, we expect to fabricate various types of chemically functionalized microfluidic devices soon.     

Novel local density of state mapping technique for low-dimensional systems

A novel local density of state (LDOS) probing method for low-dimensional electron systems is proposed. By applying a two-dimensional fast Fourier transform to a real-space image obtained by scanning tunneling microscopy (STM), visualization of a complementary image in k-space can be realized. Especially, low-dimensional Fermi contours can be extracted by applying the k-space imaging to real-space images containing sufficient LDOS information around the Fermi level. To realize a more enhanced LDOS visualization in both spaces, we have proposed the use of special materials for STM tips, which have relatively large LDOSs at the Fermi level. To demonstrate this idea, several kinds of STM tips (Ag, Au, W and Nb) with different types of LDOSs were developed. An Au(111)-(22 x square root(3)) reconstructed surface, where Shockley surface-state electrons form a nearly free electron gas, was selected as a test sample for the LDOS extraction. Visualization of standing waves in the surface LDOS modulated by herringbone reconstruction was attempted using the various types of STM tips. Significant effects of the LDOSs of the STM tips were clarified.     

Construction of harmonic map flows through the method of discrete Morse flows

By the method of discrete Morse flows, we construct the Morse flow of harmonic map from a Riemannian manifold with measurable and bounded metric into that with Alexander non-positive curvature. The construction is directly derived without isometrically embedding of the target manifold into Euclidean space. Our method will be in force in the case, as treated in [11], where a target manifold has the bounded positive curvature.     

Estimation of acoustic emission source waveform of fracture using a neural network

The applicability of a neural network to acoustic emission (AE) is presented. It is shown that the shape of the simulated source waveform using piezoelectric ceramics is steplike, similar to that of mode I crack extension, and its rise-time can be varied by the resonance frequency in the thickness direction. The results imply that the simulated source can provide learning waveforms for the network. Actual AE waveforms were also acquired by conducting a tensile test of a chevron-notched graphite specimen. It was demonstrated that the appropriate source waveform associated with mode I crack extension was successfully determined by the network taught with simulated waveforms.     

High coercivity in melt-spun SmFe10(Ti,M)2 ribbons (M=V/Cr/Mn/Mo)

Magnetic properties of SmFe₁₀(Ti,M)₂ melt-spun ribbons were studied, where M is V, Cr, Mn, and Mo. The ribbons (M=V/Cr/Mo) quenched at 20 m/s exhibit the high coercivities of 4.2-5.5 kOe. Annealing the ribbons quenched at 40 m/s enhances their coercivities in the range of 5.9-10.0 kOe. In particular, SmFe₁₀ (TiV) and SmFe₁₀(TiCr) ribbons yield coercivities of 10.0 kOe and 7.9 kOe, respectively. This is the highest value among the reported melt-spun ThMn₁₂-type structure ribbons. The importance of Sm atmosphere during annealing in minimizing the Sm evaporation from ribbons is also demonstrated     

Generic Guiding Law Between Irreversibility Field and Anisotropy—Chemical Control of Critical Current of High Temperature Superconductors

Systematic studies on the irreversibility field H _irr, and anisotropy factor ² of high temperature superconductors (HTSC) were performed using single crystals with high quality. The generic scaling law have been found to hold for all the HTSC systems examined, i.e., H _irr[Oe]=4×10^7–2 (1–T/T _c)1.5 at T0.7T _c. In addition, of each HTSC material is roughly expressed as 2=2 exp(0.78d[Å]) at the carrier optimally-doped state. Based on the generic scaling law, the behaviors of the variously doped superconductors, such as Bi(Pb)2212 and Hg(Re)1223, are discussed in terms of the critical current.     

Fundamental studies on chlorine behavior as related to zinc electrowinning from aqueous chloride electrolytes

Measurements were made on the transport and equilibrium properties of dissolved chlorine in aqueous HC1, HCl-ZnCl₂, HCl-MgCl₂, and water. These measurements included solubility, absorption rates during bubbling, stripping rates during nitrogen bubbling, and cathodic reduction rates. The solubility of chlorine was found to be affected by speciation into aqueous Cl₂, HC1O, and C1₃ −. With increasing HCl concentration, the solubility of chlorine decreased to a minimum at 0.2 mol dm⁻³, followed by a slow and linear increase. Metal chloride salts depressed the chlorine solubility approximately in proportion to concentration. Mass transfer of aqueous chlorine was found to support a current of about 100 A m⁻² from a chlorine-saturated ZnCl₂-HCl solution under typical zinc electrowinning conditions. Comparisons with published zinc electrowinning papers indicate that air sparging would eliminate dissolved chlorine sufficiently to remove the need for diaphragm cell separation of dissolved chlorine, insofar as current inefficiencies due to cathodic chlorine reduction are concerned.